The control of procellagen synthesis in cell-free extracts derived from chick embryo muscle will be studied in order to determine whether the abnormally high collagen synthesis seen in human X-linked muscular dystrophy is due to a change in the initiation of protein synthesis. Other experiments will be aimed at testing whether the denervation of rat gastrocnemius and soleus muscles leads to changes in ribosomal protein synthesis like those seen in Duchenne muscular dystrophy. Attempts will be made to simplify the in vitro protein syntesis test for heterozygotes of Duchenne muscular dystrophy.